The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In modern internal combustion engines, particularly those employing turbochargers and variable valve timing, a certain percentage of air entering the engine through the intake manifold will pass completely through the engine cylinders, i.e., from the intake valves to the exhaust valves, during the intake stroke and will thus not participate in the combustion cycle. This can occur during high cam (and valve opening) overlap on boosted applications, especially at higher pressure ratios. This untrapped air passing completely through the cylinder is referred to as scavenged air.
While one might perceive such scavenged air, in the first analysis, as undesirable, it does allow the turbocharger to spool up more quickly, thereby improving pressure boost response. The true difficulty of scavenged air is that engines which operate in a scavenging mode, not surprisingly, also operate in the more conventional, non-scavenging mode in which all the air passing through the intake valve is trapped in the cylinder for the compression and power stroke, after which it is exhausted. While such engines typically employ separate control models for operation in the scavenging and non-scavenging modes, the transition between the non-scavenging mode, typically at lower RPM's, and the scavenging mode, at higher RPM's, can be abrupt and create discontinuities in both the monitoring and operation of fuel, air flow and ignition systems.
Thus, there is an acknowledged problem in internal combustion engines and controls which operate in both scavenging and non-scavenging modes. The present invention addresses this problem.